Those well versed in the search game can easily chronicle how the act of social linking gave way to the link economy. When Google gave quality links value, the game was all about how to get them. Can't get favorable external mentions? Swap links. Google discounting reciprocal linking? Join up in a large, elaborate interlinking scheme that passes PageRank to members. Oh, but you knew Google would get wise to that too, didn't you? And that they would introduce Other Ranking Factors and spam tests to try to get the real good stuff to bubble back up to the top again?

Now, word's out that Yelp management won't take such schemes lying down when it comes to local business owners banding together to write positive reviews in order to boost each others' reputations and rankings in category listings. The business owners protest; Yelp sticks to its guns. Is it Orwellian? Consumer friendly? Or should anyone get their shorts in a knot about a few glowing reviews of the local pull-taffy-and-bubble-tea emporium? I mean, who doesn't like taffy?

Well, maybe it's a bit of both. Google's practices and philosophy are very similar. To paraphrase: "We reserve the right to torch your rankings if we suspect any shenanigans. Sorry."

It all boils down to the fact that neither Google nor Yelp ratings are literally "correct." Both are open to interpretation and game-playing. However, in a more comprehensive sense, businesses can develop strong reputations by being visible on these properties, and they can do so without cheating. For now, the publishers' attempt to stem cheating will be tinged with arbitrariness. Some howls of protest might be legit. Longer term, these sites will allow for deeper probing into claims: peers will be able to find peers and get a better sense of what's real.

Make no mistake about it, though: relevancy rankings, and business ratings and reviews, are serious business. Consumers depend on them. Businesses with strong ratings often deserve them. It would be a huge shame if the Googles and Yelps of the world were forced to give into scaremongering about their imperfect technology; perhaps left to plaster For Entertainment Value Only across their pages, like some cheap carnival psychic.

In one of the paid search sessions yesterday here at SES London, one audience member gave his account of the "death spiral" that seems to afflict certain keywords in his AdWords account. "I wake up and Google's asking for £2.50 for a keyword, so I raise the bid. The next day, they've put it up to £5.00. (etc.)."

Obviously this is a signal that the relationship between this keyword, ad, and landing page is seen as "very low quality."

So I asked roughly what industry he was in - turns out it's related to debt relief. The keyword in question? "Lottery tickets." Yup, I thought to myself - in the new Quality Based Bidding regime, that's seen as just too far off the mark in terms of relevancy to the service being offered to the consumer.

This might have fallen flat at any stage of AdWords history, though, by virtue of the low CTR it would likely attract. A "popular culture" type word (people looking up lottery listings is a very common navigational function) will be so high volume that the proportion of users who are thinking "transactionally" and willing to check out an offer is so low that it will lead to a CTR that is below any threshold of reasonability as far as today's PPC auctions go.

You admire the lateral thinking here: people desperate to dig themselves out of debt might be more inclined to buy and look up info on lottery tickets. If so, then an advertiser should probably try to get placement on relevant websites through direct media buys and various banner and text ad targeting tactics (one being Google's Site Targeting option).

But you'll have much more trouble doing this type of "loose targeting" if you're using AdWords and Yahoo Search Marketing, unless of course you have a strong, established CTR and user experience history.

So is an ad for debt relief next to search engine results for lottery tickets really "low quality"? Yes, moderately so, because in the user's eyes, search is special. They want even the ads to be tightly targeted, or let there be no ads at all.

Google is no doubt going to continue to modify the Quality Score algorithm to fine-tune the balance between advertisers' needs and the user experience. Stay tuned.